With the increasing popularity of reusable soda bottles and the like, it is important that the bottles be resealed after each use. Adequately resealing the bottle is essential to maintain the carbonation in the liquid. In order for this to occur, the cap must create an air tight seal with the bottle to maintain an increased pressure therein. In the alternative, if the pressure is allowed to escape between the cap and the bottle, the soda will loose its carbonation.
Various attempts have been made to provide a bottle cap which will maintain the increased pressure in the bottle. One such bottle cap, which is currently available, has a soft rubber or plastic liner provided inside an outer shell. The outer shell is dimensioned to fit over the threads of the bottle, while the liner cooperates with the threads. This cooperation of the liner with the threads provides a seal therebetween, thereby theoretically preventing the flow of air into and out of the bottle. The shell insures that the liner is protected and maintained in place. However, this type of cap has been proven inadequate. The liner must be comprised of material which is rigid enough to maintain a shape, while being resilient enough to deform about the threads of the bottle. As the liner is subject to the temperature changes, associated with being moved into and out of the refrigerator, the liner expands and contracts at a different rate than the bottle (due to the different materials). This causes passages to be provided between the threads and the liner, through which air can escape, thereby allowing the pressure to escape from the bottle. Another problem associated with bottles caps of the prior art, is that the liner has a tendency to deform with use. Consequently, the more the cap is used, the less effective the seal becomes. The deformation of the liner provides passages through which air can flow.
Another bottle cap which is available in the market has a shell which has cap threads provided to cooperate with the bottle threads. In order to provide an air tight seal, a thin layer of material, which is manufactured from rubber or soft plastic is positioned on an inside surface of the cap to cooperate with the top of the bottle. The same material also extends between the cap threads, such that as the cap is positioned on the bottle, the material between the cap threads will cooperate with the bottle threads to prevent the passage of air therebetween. However, this cap suffers from the same inadequacies as described above. However, the problem of an inadequate seal occurring is more pronounced in this cap. Due to the thin layer of material deforming after only a few cycles, the seal will fail.
It would therefore, be beneficial to provide a bottle cap which, under any conditions and over many cycle would prevent the flow of air from the bottle, thereby maintaining the required pressure in the bottle. In order to insure that this seal will remain stable over time and changing conditions, it would be beneficial to obtain this result without the use of a material which expands and contract at different rate as the bottle.